Condensed dialing arrangement



Dec. 8, 1964 o. H. wlLLlFoRD 3,160,713

CONDENSED DIALING ARRANGEMENT Filed Aug. 22, 1962 4 Sheets-Sheet l A TTORNEV Dec. 8, 1964 o. H. wlLLlFoRD CONDENSED DIALING ARRANGEMENT 4 Sheets-Sheet 2 Filed Aug. 22, 1962 momo .zzou

/NVENTOR B 0. H. WILL/FORD N ...Sk

ATTORNEY Dec. 8, 1964 o. H. wlLLlr-'ORD CONDENSED DIALING ARRANGEMENT 4v Sheets-Sheet 5 Filed Aug. 22, 1962 /NVENTOR BV 0. H. WILL/FORD A TTORNEV Dec. 8, 1964 o. H. wlLLlFoRD CONDENSED DIALING ARRANGEMENT 4 Sheets-Sheet 4.

Filed Aug. 22, 1962 m n Rm m mu H mm A N /H. O. V B .2: l@ mmooumo GNR United States Patent O 3,160,713 CNBENSED BEAUNE ARPJNGEMEN" Oscar H. Wiilifnrd, Bronx-ville, NX., assigner to rell '.llelephone Laboratories, incorporated, New York, NSY., a r. or,-,.\eration ef New York Filed Aug. 22, 1962, Ser. N 218,718 12 .Claims iCi. NSF-l) This invention relates to abbreviated dialing of telephone directory numbers and more particularly to a system enabling a PBX extension user to dial a frequently called telephone number by using fewer digits than are normally required.

The advent of nationwide dialing has made ngertip access to literally tens of millions of telephones a reality. However, when the caller has occasion to re-dial the same seven, ten, or thirteen digit number several times during the day, he is less likely to appreciate the ease and simplicity of direct distance dialing as compared to prior toll operator systems. A particularly noticeable instance of s uch usage may be found to occur in almost any business organization having a private branch exchange through which calls are repetitively placed to the sameV suppliers, material men, customers, outlying factories, and branch ofces. While the needs of different business organizations vary as to the number and location (area-wise) of such frequently called telephones, a trahie analysis will usually show that for a medium to large size business organization, such as might utilize a PBX of the size and complexity of the Western Electric 701 type, a repertory of about fifty telephone numbers would satisfy the requirements of most customers.

VThe mitigation of dialing fatigue has heretofore been attempted by resorting to either of two approaches, one employing repertory dialing telephone sets and the other employing random-access magnetic drum circuits at the central oice. While both such systems are satisfactory, the first requires the use of a fairly costly unit of apparatus on a per-extension basis and the second involves a sophisticated electronic apparatus the maintenance and installation of which poses somewhat of a problem in existing central oiiices utilizing conventional switching train or crossbar techniques.

Because of the high community of interest existing among extension users, the private branch exchange appears'to be a particularly attractive area in which to explore the application of common equipment methods to reduce customer dialing effort. It is 'to be anticipated that in addition to cutting down the numberV of digits associated with calling a particular telephone number, the elimination of the need to dial the directing digit 9 and the need to wait for a second dial tone vthat is usually associated with this procedure would be considered advantageous by PABX customers. A workable scheme should -involve the installation at thetprivate branch exchange of simple, easily serviced, and inexpensive equipment, and should be compatible with outgoing trunk circuits. Such equipment as may be required at the central oilice to cooperate with the foregoingrshould be available for use with the corresponding equipments at a number f remote private ybranch exchanges in such Va manner that neither the concept of common control, which characterlhlg Patented iDec. `8, 1964 ice easily be altered and which may function on a common equipment basis.

It is another object of .the present invention to eliminate the need for dialing an initial directing digit, such as the digit 9, on atleast some outgoing calls.V

Itis another object ofthe present invention to eliminate the need for an extension user to await second Vdial tone on at least some outgoing calls. i

The foregoing and other objects are achieved in accordance with the principles of the present invention, in one illustrative embodiment, by including aV plurality of auxiliary trunks on at least'oneotherwise unassigned level of the first selector of a private branch exchange switching system, the level on .the selector wcorresponding to the first digit of a condensed dialing code. Each such auxiliary trunk is associated with a corresponding trunk on the selectors level of outgoing trunks, forV example by multipled sleeve terminals, so that an auxiliary trunk can be lseized by the selector only when its corresponding outgoing trunk is idle. The second and third digits f the'condensed dialing code are transmitted over the selected idle auxiliary trunk to a connector type switch which selects a terminal on its bank having coordinates corresponding to the transmitted second and third digits. A pair of 'row and column relays are activated in accordance with the selected terminals coordinates and contacts of Ythese lrelays control a multi-frequency outpulser which transmits the digits of thefconde'nsed ydialing code to the central oilice over a data link individual to the PBX. At the central ofhce, the data links, from the various PBXs having condensed dialing service, each terminate in a `respective line circuit. The line circuit seizes an available receiver through a receiver-sending link. The digits outpulsed by the PBX are entered in the receiver vand enable the receiver respectively ,to ,select a `crossbar switch, to

' operate its horizontal selectV and vertical hold magnets,

izes central office installations, nor the concept of interl communication, which characterizes PBX switching installations, will in any way be jeopardized.

Accordingly, it is an object of the present invention to provide a simple and inexpensive arrangement for permitting extension users to employ abbreviated or condensed dialing of frequently called telephone numbers. It is another object of the present invention to provide a translator whose repertory of telephone numbers may and to select a contact of its operated crosspoint. The selected contact is associated with a code point from which a jumper threads a Word-organized array of transformer cores yin accordance with the conventional telephone directory number digits corresponding to the condensed dialing code. The 4auxiliary ltrunk at the private branch exchange has in the meantime applied a calling bridge to its associated outgoing trunk to place itin Vthe dial tone state. This state having been obtained, the

,telephone directory number digits corresponding to the condensed dialing code are Atransmitted back over ,the data link to the private branch exchange and applied by the auxiliary trunk-to the associated outgoing trunk, thereby to operate the outward switching Ynetwork of the central othce in the conventional manner. At the completion of outpulsing of the directory number digits, Vthedauxiliary trunk cuts through a communications connection to .directly connect the tip and ring associated with the auxiliary trunk appearance on the condensed dialing level ofthe first selector with the tip and ring of the associated outgoing trunk on the selectors level of outgoingtrunks.

Accordingly, a feature of the present invention is an auxiliary trunk circuit which receives condensed codes transmitted by a PBX station, obtains the conventional telephone numbers corresponding thereto, and provides for the transmission of these numbers `to vthe central Vofiice over the outgoing trunks with whichrthePBXris normally equippedf Another Vfeature of the present invention is a data link and translator accessible to the auxiliary and outgoing trunk circuits so that the condensed codes are Vtransmitted from the auxiliary trunk over the datarlink' tothe translator and the corresponding telephone numbers'are transmitted from the translator back over the data link to one of the outgoing trunks. A

K digit designation.

Another feature of the present invention is an auxiliary trunk circuit for seizing and placing in the dial tone state an idle ninth level trunk circuit during the dialing of a condensed dialing code which code need not include the digit 9.

According to a further aspect of the foregoing feature, the auxiliary trunk circuit obtains an expanded code corresponding to the condensed dialing code and transmits the expanded code to the central ofiice over the seized ninth level trunk.

Another feature of the present invention is a circuit for selecting auxiliary trunks with one digit of the condensed dialing code and recombining that digit with the remaining digits of the dialed code to increase the number of nonconflicting codes that can Ybe composed from these remaining digits.

A further feature of the present invention is'a crossbar translator circuit in which'a `multicontact crosspoint is selected and one contact of the selected crosspoint energized in accordance with a condensed dialing code.

Still another feature of the present invention is a first circuit for associating outaoing and auxiliary trunks on different levels of the first selector of an outward switching train so that each reliects the busy and idle states of the other, and a second circuit which Vdirectly interconnects th'e different level appearances of these trunks after the completion of signaling thereover.

The foregoing and other obects and features may become more apparent by referring now to the drawing in which:

FIGS. 1 and 2 show that portion of the circuitry of the present invention that is located at each PBX;

FIGS. 3 and 4 show that portion of the circuitry which advantageously may be located at the remote central oftice; and in which FIG. 5 showshow FIGS. 1 through 4 shall be assembled. Y The private branch exchanges 10), 201i (FIG. l) are assumed, for the sake of illustration, to be of the conventional step-by-step type. plurality of extension stations 101, each of which is assigned an extension number having, for example, a four- When an extension user at the PBX desires to initiate a call he releases the subset switcnhook and awaits dial tone. A line finder 102, associated with an idle selector 193, locates the line terminals of the calling subset and applies dial tone furnished by the selector. In response to dial tone the extension user proceeds to dial the called number. The wipers (not shown) of the first selector 103 are stepped by the first dialed digit to arcorrespondingly numbered level of terminals on the selectors terminal bank. Before the second digit is dialed the first selector causes its wipers to hunt acrossY the level and to seize an idle set of the terminals appear-` ing on that level.

In most conventional PBX switching systems, the terminals appearing on the various levels of the first selector are terminals of trunks, that is, they are not directly 'as- 4dialed by the calling extension user.

Conventions have grown up regarding the assignment of trunks to the levels of the first selector. ln accord- .ance with one such convention, terminals of the tenth level are assigned to local switchboard operator or local attendant trunks, terminals of the ninth level are assigned to outgoing or central ofce trunks (such as trunks 196, 107, 108, 109) and terminals of levels 1 through are assigned either to local completing (intra-PBX) or to tie trunks. ln most installations there will be at least one and usually two or three of levels 1 through S which are EachV such PBX includes a unassigned. Let it be assumed in the following description that levels l through 7 have not been assigned a conventional PBX usage.

However, in accordance with conventional PBX operation, when the extension user,V after receiving the dial tone furnished by the first selector, dials the directing digit 9, the first selector rises to the ninth level and hunts across the trunks 106, 107', 108, 109, and any other trunks appearing on that level until an idle one is found. The seized trunk has its tip and ring bridged by the calling extension station and this bridged condition constitutes a service request to the central otlice outward switching network 306 (FIG. 3). In response'thereto, a second dial tone is furnished the extension user, this time by the central ofrce network 360, and thereafter the extension user may proceed to dial the seven, ten or thirteen digits of any telephone number assigned in the nationwide dialing system.

While the dialing of seven-digit and ten-digit telephone numbers is not unduly burdensome when calls are made on an occasional basis, studies have shown that the repeated dialing of the same lengthy series of numbers, rather than educating or increasing the proficiency of the dialer, results on the contrary in an increase in dialing errors. Whatever the underlying reasons for this may be, it is evident that dialing errors will be materially reduced if the length of such repeatedly dialed numbers is reduced. The present invention is directed to a circuit which enables the user of PBX extensions to place calls through the outward switching network 364i of conventional central ofiices without waiting for the return of second dial tone and by dialing fewer digits than are normally required to be dialed to operate the switching network 300. lt is considered that this feature will improve that area of telephone service that is most susceptible to dialing errors because of high level traflic.

At this point it may be well to consider the characteristics of the condensed code to be employed. Each business organization which generates suflicient telephone trafiic to warrant the installation of a private branch exchange will normally be found to make calls to a particular group of telephone numbers on a sufliciently repetitive basis to warrant these numbers being treated specially. rl`he average size business organization served by a private branch exchange system in which the extension stations are assigned four-digit designations may have about fty Vsuch frequently calledV numbers and it is these numbers kthat will form the repertory of numbers for which condensed dialing codes should be assigned. Although a repertory of lift or even one hundred condensed dialing codes, could be designated by the use of merely a two decimal digit condensed dialing code, a three-digit code K is preferred for this purpose because it allows for simpli- `sociated on a one-for-one basis with particular extensions y lication of the translator that is to be used in common by each of the different PBXS, as will hereinafter be more fully explained. i

Let it be assumed that the extension user at subset 101 desires to place a call to a supplier who is called on a sufiiciently repetitive basis to warrant his being assigned a three-digit condensed dialing code, such as mode 762. The extension user removes the receiver from the switchhook of subset fatti .and receives normal dial tone over circuits (not shown) that are customarily associated with the line finder 1d?, andthe first selector 103 of his private branch exchange switchingsystem idf?. The extension -user-dials the first or hundreds digit of the condensed dial code which digit is assumed to be 7. In response to the dialing of digit 7,? the first selector steps its Wiper (not shown) in the normalmanner to the seventh level of terminaisonV its terminal bank. The first selector 103 then in the normal manner steps across the terminals on the seventh level, examining the sleeves until it finds one that is not grounded indicating that the corresponding Ytrunk is idle. The selector stops its wiperropposite the terminals of the idle trunk and makes the trunk busy by applying ground to the sleeve terminal.

Each trunk on the seventh level of the rst selector has its sleeve terminals such as sleeve terminals S71 and S74 of the iirst and fourth position trunks, connected to the sleeve terminal of a respective trunk on the ninth level of the selector. Advantageously, the trunks appearing 1n the iirst through iitth positions on the ninth level are allowed to perform their usual functions While those in .the sixth through ninth positions may be chosen as those whose sleeve terminals S96 through S99 will be connected to the sleeves S71 through S74 of the seventh level trunks.

ln this manner dial 9 calls Will normally attempt to select ninth level trunks in the first preferred positions while compressed dialing calls will test those ninth level trunks appearing in subordinately-preferred positions that are not normally selected for use `by dial 9 calls. The system thereby retains exibility in that conventional or noncompressed code .dialing calls may continue to be made in the usual manner even over trunks selectable from the condensed dialing levels ot the iirst selector.

Let it be assumed that, in the condensed dialing code call .being made, the iirst trunk on the seventh level or" selector M53 is selected because its sleeve and the sleeve S96 of ninth level trunk 16S reflect an idle condition. Selector 163 in the usual manner then applies a ground to `sleeve S71 which ground is continued over to sleeve S96 to prevent trunk ll from being seized at its multiple appearance on any ofthe other first selectors (not shown) normally used. Subset lill presents a calling bridge to the tip and ring terminals T71, R71. The calling bridge condition is continued over the back contacts of relay D7 in cable C71, and the Winding of relay 7HN7 to cable C71 and connector 291 in FIG. 2.

Connector 201 may advantageously be any of the well- .known types of step-by-step switches which advances its Wipers up to a level on its terminal bank under the direc- -tion of one sequence of dial pulses and which rotates its Wipers along the level under the direction of a subsequent sequence of dial pulses. In accordance With the mode ot operation envisioned herein, the dial pulses associatedv with the second digit of the compressed dialing code dialed by ,the extension user step the Wipers (not shown) of connector 231. Assuming the condensed dialing code is 762, vthe Wipers of ,connector Zll will b e stepped to the sixth level `of terminals on the connector bank. T he third digit of the compressed dialing code steps the wipers of .confnector 2M along the selected level. In theA assumed cornpressed dialing code the Wipers will make contact with the second set of terminals on the sixth level of the con- -nector bank. For the sake of simplicity, however, only four terminals are explicitly shown on the bank of connector 261 and these are the iirst and last terminals of the iirst and last rowand column of terminals on the con- .nector bank. ln a conventional connector there are ten levels or rows and ten rotary positions or columns of terminals. The terminals on the bankof connector 261 Vare :numbered in accordance with the sequence of dial rpulses required to step lthe wipers of the connector to each of the terminals. Thus, the iirst terminal on the lowest level of the bank is terminal l`l and the last terminal on the lowest level is terminal l-ltl, whereas the iirst .terminal on the highest row of the connector bank is terminal lil-1 and the last terminal on the highest bank Vis terminal lil-lil.

When the second and third digits of the compressed dialing code have stepped the Wipers of connector Zbl to a particular terminal on its terminal bank, one of the row relays ROWl through ROWl and one of the column `relays CCLl through COLltl will be operated by the Aground supplied to the selector terminal by the Wiper of connector Ztll. Advantageously, the particular Wiper of .connector Zbl that is used vto apply the ground may be .the sleeve Wiper (not shown) Similar row relays RUWl through ROWltl and similar column relays CGLl through COLIG are associated with connector 2tlg..

Contacts of relays ROW?. through ROWitl are asso- `ciated with respective ones of the ten TNG-1)) buses and contacts of relays COLl through COLlll are associated with respective ones of the ten Udall) buses. The hundreds digit was previously registered on one ofthe HO- buses by the operation of the hundreds digit regenerating relay incident to the operation of connector 201i. In the above example, the yoperation of relay 7HN7 at one of its make contacts grounded bus H7. Another make contact ot relay HN grounded the TH bus. In the above eX- arnple, when connector 2M positions the Wipers opposite the second terminal on the sixth row, row relay ,ROW and column relay COLZ, though not explicitly shown in the drawing, would be operated and their make contacts would ground `the TN6 and the U2 buses.

When connector 2&1 has stopped at the above-mentioned second terminal on the sixth row, a C relay (not shown) is released in the connector. The release of the C relay at the completion of rotary stepping is a well-known function of `connector circuits, and accordingly the circuits therefor need not be shown in detail. A spare Contact on this relay is associated with `lead C261 to ground this llead when Vconnector 205i has `completed rotary stepping. Lead CZtlt grounded `activates preference lock-out circuit 2de so that the ground applied to lead Cibi may be extended ,over back contact-D3'.I to operate connector relay CON?, provided -that :n o other connector, such as connector ZiZ, has grounded its corresponding lead CZlZ. As many connectors ,2011, 202, et cetera, may be provided as there are subordinately `positioned outgoing trunks such as 193,109. Preference lock-out circuit 2M advantageously may comprise any of the types Vof such circuits well yknown in the art, some of which are described, for example, in the book entitled The Design of Switching Circuits by Keister, vRitchie and Washburn, published by D; Van Nostrand Company, 1951.

The connector contacts yof connector relay CGN connect .the TH, H, TN, and U digit buses to outpulser 1132 and one of its .make contacts completes one of the possible operating path for relay CONA which in turn operates. Another make Contact of relay CQN7 prepares an operating path for relay D7 but relay D7 does not operate at this time.

The three-digit code dialed bythe extension user, plus the fourth or TH .digit added by the contacts .of the hundreds digit regenerating relay 7HN7, are entered in outpulser 112 by the digit buses over connector contacts CON7. The registration of these four digits is veried in ,outpulser 112 in the conventional Vmanner by the operation of a read-in Vcheck relay, such as relay :RIK (FG. l). Details of circuitry for registering digits and for operating a read-in check relay are omitted in view of their conventional nature. Relay RIK operated, at one of its make contacts, completes an operating path to the windings of relays TR and CBCO. Another make contact of relay RIK bridges the windings of outpulser 112 supervisory Vrelay Sl;

Relay R operated connects data link D to the output of outpulser llZ. Relay TR operated locks itself and relay CBC() to ground in series with a back contact of relay AFT and a make contact of relay CONA. vRelay CBCO operated at its make contact applies a-calling ,bridge including a back contact of relay AFT across the tip and ring conductors of the left-hand side of data link l Dlitl. The left-hand side of data link Dill@ is at tlr's tirne isolated from outpulser M2 bythe operated back contacts of relay TR. The tip and ring 'leads from the calling ,bridgeV at the left-hand side of Vdata link Dld@ are continued over make contacts of connector CON, cable CCl, and back contacts of relay D7 to ythe tip and ring conductors of trunk 36S. Application of this calling bridge to the tip and ring leads causes trunk yll to place the central oliice outward switchingnetwork 3G@ in the dial tone state. in FIG. 3 an illustrative portion Vceiver-sender link Elli.

i (i.e., a typical incoming trunk, incoming register, and incoming register link IRL) of the outward switching network 369 is rshown schematically, When the calling bridge including make contact CBCO and back contact AFT (FIG. 1) is initially applied between the tip and ring leads of trunk M58, relay CT in trunk 1633 is operated in series with back contacts of relay H1. Relay CT operated at its make Contact applies ground to the ring lead of trunk 133 on the central omce side of cut-through contact H1. This ground operates the trunk L relay at the central oiiice Sill). Work contacts (not shown) of the trunk L relay operate the incoming register link IRL to assign an idle incoming register to the trunk. The assigned incoming register of central oiiice 369 returns ground in series with the dial tone coil to the tip conductor. Relay H of trunk S operates in response to vthe ground applied by the assigned register and operates relay HA in series with an operated make contact of connector CONI'. The operation of relay HA therefore signies that the central office originating switching network 3G@ has been placed in the dial tone state. However, this dial tone is not audible to the extension user and does not in any way delay bis dialing of the threedigit condensed dialing code. Relay HA operated prepares an operating path to the Winding of relay AFT.

Relay H operated operates relay Hl which releases relay CT. Relay H operated also cuts through the tip and ring conductors from the central ottico side of trunk 108 to the PBX side of trunk N3. The release of relay CT removesthe ground that was formerly applied by a make contact of this relay from the ring conductor but the register L relay is not released because .its operating path is maintained by the calling bridge. In this regard it is assumed that Vthe make contacts of relay H1 in series with the tip and ring conductorswill make slightly earlier in time than the Hl back contacts in series with the winding of relay CT break so that an inadvertent open will not be transmitted to the central office register and prime it to respond to dial pulses instead of the multifrequency signals intended later to be forwarded it. Relay S operates in series with the loop current and in turn operates relay S3. which removes the winding of relay H from thel tip conductor for improved l transmission. Relay S1 operated also provides a hold- 1ng ground for relay H1.

cordingly, the dial tone state is obtained only a very short time before the actual transmission of the translated code to the central ofiice switching system 312'?! is to commence.

Returning now to the operation of outpulser lZ and 'data link D106, the bridging of the windings of polar relay Si by a make contact of relay Ril( constitutes a calling bridge condition that is carried forward over make contacts of relay TR to the right-hand portion of Vdata link Dltltl. Data link D16@ terminates in a line circuit 3 1 (FIG. 3) and data link DES@ of PBX 2% terminates in a corresponding line circuit 3 2.V The line circuits for each PBX data link have a respective appearance in re- These line circuits as well as link 3M may adantageously be of any well-known type. The battery and ground returned by the A relay of line circuit 3 1 does not operate polar relay Sl. However, when receiver-sender link 391 connects an idle receiversender set such as 363, the receiver supervisory relay RC returns battery and ground that is of the proper polarity to operate outpulser supervisory relay Si.

Relay S1 operated at its work contacts (not shown) enables outpulser 112 to transmit the TH, H, TN, and U digits over data link D18-Il to the receiver portion of the assigned receiver-sender set S33. Advantageously, outpulser i12 may include a multifrequency generator operable in series with the loop current, as described in the article entitled Tone Ringing and Pushbutton Calling by L. A. Meacham in the Bell System Technical Journal, March 195 8, pp. 339-3 60. However, instead of the contacts of the frequency selecting pushbutton array PB being manually operated, they advantageously may be operated in sequence by the registering relays (not shown) that are associated with the TH, H, TN, and U digit buses. At the completion of outpulsing, outpulser M2 read-out check relay ROK is operated in the usual manner. Relay ROK is advantageously made slow operate relative to the operating time of read-in check relay SRC at the receiversender set 393.

Relay ERIC operated signities that the receiver portion of receiver-sender set 303 has received four digits, at which time its operation transfers the tip and ring leads extended through link 391 to the sender portion of receiver-sender set 363. In addition to its transfer contacts, relay SRTC controls connector contacts, similarly designated, to connect the output of the receiver portion of receiver-sender to cable 396 and the input of the transmitter portion to cable 337 and to lead 30S. Cables 3% and 367 and lead 368 are associated with the apparatus for translating the condensed dialing codes into conventional telephone directory numbers shown in FIG. 4, which apparatus will be hereinafter more fully described.

Returning now to FIG. l, outpulser 112 read-out check relay ROK operated reverses the connections to the Winding of polar supervisory relay Si. Polar supervisory relay Sl is now released because the battery and ground potentials applied over the Winding of marginal polar supervisory relay TS in the sender portion of receiver-sender set 393 are opposite to that formerly provided by the winding of receiver supervisory relay RC. Relay ROK operated and relay S1 released complete an operating path to relay TC which operates, signifying that the translator transmitter, i.e., the sender portion of receiver-sender 303, has been connectedA Relay TC operated at one of its l make contacts completes an operating path (made available over operated make contacts of relays HA and ROK) to the winding of relay AFT. Relay AFT now oper tes and at its back contact removes the calling bridge priorly inserted across the extended tip and ring conducrtors of trunk TQ3.

Y relays TR and CBC@ which release.

tended conductors of trunk 363.

Relay AFT operated also opens the locking path for Relay TR released at its back contacts connects data link D to the extended tip and ring conductors of trunk 19S. Relay AFT operated locks to ground in series with the back contacts of relays D7 and Dit?. The central oli-ice outward switching network continues to be held in the dial tone state, after the aforementioned calling bridge is removed, by the battery and ground applied over the windings of marginal polar relay TS in the sender portion of receiversender se* ln this connection it should be noted that the battery and ground applied over the windings of relay TS aids the battery and ground polarities respectively applied over the winding of the register L relay and the dial tone coil in switching network 36). The combined battery'and ground supervision is sucient to enablemarginal polar relay TS in the sender portion of receiver-sender 3633 to operate. Relay TS operated at its Work contacts (not shown) permits the sender to outpulse over data link D169 the digits of the seven, ten, or thirteen digit code that will be furnished the sender by the translator apparatus in FG. 4.

When relay TR released, as described above, the Windings'of series relay M (FIG. l) were inserted in series with the Vtip and Vring between the data link and the exl Relay M operates in response to the high current in the loop including the data link and the central oice trunk due to the aiding potentials of the battery and ground supervision. Relay M operated, at its make contact operates relay MA and at its back Contact opens the operating path to relay D7 that would otherwise vbe completed by the operation of relay MA, preventing this relay D7 from being operated at this time. lViren the sender ot receiver-sender set fall?, has completed outpulsing, the translated code relay END is operated, removing battery and ground supervision from the windings of transmitter supervisory relay TS, and substitutes a holding bridge across these windings. The loop current is thereupon reduced sufficiently to allow series relay M to release. Relay M released at its back Contact restores the Voperating path to the winding of relay D7. Relay D7 operates and 'locks to sleeve ground before its operating path'is broken by `the release of slow release relay MA. `lelay B7 operated opens the locking path for relay AFT which releases. Relay D7 operated disconnects vthe extended tip and Vring ot trunk circuit ldd from data link Dill@ and lconnects vthem directly to the tip and ring terminals T71, R71 ofthe seventh level condensed dialing trunk selected by the extension user. The data link Vis thereupon restored to normal and may again be utilized when outpulser 112 is reseized by another extension user having dialed an abbreviated dialing code.

Referring now to FIG. 4, there is shown the translator for responding to t'ne four-digit condensed dialing code obtained by one ot receiver-senders Sll, 3553 (FIG. 3) and for providing to the ,sender portions thereof the corresponding repertory word, ie., seven, ten, or thirteen digit telephone number. The illustrated translator cornprises two, 'twenty vertical, six-wire lcrossbar switches 4lll, 462, a decoder 456, a code point Veld 46), an array of magnetic transformer rings 479, andan output stage 4gb. Additional twenty vertical crossbar switches may be added to increase the number assignment exibility if desired.

With the use ot only two, twenty vertical crossbar switches, forty verticals are available and each of the forty verticals may be Vassigned to tlesignate Vthe titty repertory translations 'for one PBX. If it is thus desiredthat all thetranslations for a given PBX should be confined (for ease of maintenance) to the same vertical, -it vis vrequired that all'the condensed dialing codes for the given PBX have the same units digit, for example. Since the units digits() through ,9 only yallefvv'for the selection ,of ten verticals corresponding to ten diierent PBXS, the TH digit 4is used to increase 'the selection by steering the outputs 'from the units digi-t -stage ot' decoder 45t? over theadditional vertical 'hold magnets of crossoar switches '4551 and 462. T o designate forty verticale in this manner four TH digit outputs wouldbe required and vthere would be tour relays inthe group of relays THQ through 'Riti'.

'On the other hand, it it is 'desired to serve orty didierent lUB'l s and not to restrict the iity condensed dialing codes per PBX in any manner, twenty crossbar switches providing a total ofour hundred verticals would be required. 'Eachunits digit would require a respective vertical and each PBX would be assigned ten verticals. VSince 'for-ty TH digits would 'be required, it would be necessary for outpulser '112 to transmit tivo-digit TH digits on a decimal basis instead of the one decimal digit iTd digit Apreviously assumed. Alternatively, outpulser 5.3.2 need generate no TH digit Vat all if each Vline circuit 3 1, et cetera, (TIG. 3) operates a respective one of forty THQ through TH' relays of FlG. 4.

lnasrnuch as the restriction oi' one digit of lthe condensed dialing codes would not appear unduly to limit thelexibility of the system, the description of the illusltrative embodiment .vill 4be continued on this basis. li `a `particular PBX should require :more than tty reper- 'tory 4codes V:which can :be selected -using `the sante units idigit, .additional units `'digits :each'capable of AVincreasing the repertory by iifty condensed dialing codes may be assigned totbe PBX When one of the receivers such as receiver 3% has been seized by receiver-sender link Sill and has received a tour-digit code transmitted to it over a data link from one of the FBXS served by the central office, its read-in check relay IBRC is operated. The operation of relay Sill@ effects the operation ot connector relay contacts in the well-'known manner. For example, assuming the receiver portion of receiver-sender set St to `have been seized and to `have received a four-digit code from PBX lull, relay Sill@ is operated upon the completion of a conventional read-in check. Relay SRlC operated at its uppermost connector contacts connects the receiver portion of receiver-sender set 533 to cable 3% and at its next lower contacts connects the sender `portion of receiver-sender set 3%3 to cable 3&7. ln addition, the lowermost of contacts SilC connects `the winding of relay END to lead When the receiver lportion oi receiversender set 3il3 is connected to cable Sitio, the four-digit code is transferred to decoder 45@ (FTG. 4). Decoder 45% responds to the TH digit to operate a corresponding one ot steering relays Tl-lll thro-ugh 'Tl-lil.

it will be recalled that the TH digit transmitted to the receiver over the data link was obtained from a contact of one ot the hundreds digit regenerating relays 7HN4 througnL '7l-IN? or llllfllsld through ltlHN. The TH digit, lin addition to the U digit, is used 'by the translating equipment in identifying the particular vertical of Vcrossbar switches dill, 4@ having the repertory of telephone numbers or each PBX. Contacts of steering relays Tleltl through THQ selectively connect the units digit outputs ot decoder 45h to different groups of the vertical hold Amagnets associated `with crossbar switches 491 and 4522 and the combination ot- Vthe operated Trl-itl Vtlnough T HG lrelays and the activated units digit output uniquely identity a vertical hold magnet. The ten TN digi-t outputs of decoder are connected to the ten horizontal select magnets of crossbar switches 431 and 492.

The iifty numbers that form the condensed code repertc-ry for a given VPBX all end in the same units digit.

These condensed code numbers may have hundreds digits chosen from the numbers 4 through 3 and tens digits chosen from the numbers 0 through 9. Accordingly, the .titty abbreviated dialing codes for the first PBX will be 401, V411, 421, 431, 441, 451, 461, 471, 481, and 491; 4501, et cetera, through 591; 601, et cetera, through d69-1; 701, etcetera, through 791; and 801, et cetera, through VThe hundreds digit outputs of decoder 459 are connected fto crosspoint contact selection relays 1C034 through CCSS. lt will be recalled that there lwill Vbe as many hundreds digits as there are levels of the first selector ll set aside for condensed dialing codes. 'lnas- -much as Athe third through the eighth levels of rst -sevlector litl conventionally may be unassigned, enough crosspoint Contact selection relays CCS4 through CCS are shown to handle all these possible hundreds digit condensed code designations even though, in FG. 1,', only levels four through seven were illustrated.

Crossbar switches 4%1, 4t2?. include a plurality of crosspoints of which only the crosspoints 4%, 4ll4, and 4&5 are shown. Each crosspoint includes v-sin contacts which and the lowerrnost ones, respectively, of the horizontal select magnets. The crossbar switches are Wired so lthat in each ver-tical column of crosspoints thetlrst contacts are wired together to a circuit controlled by orosspoint contact selection switch @C34 and the last Contact of each crosspoint in the column is controlled by crosspoint sacarte contact selection switch CCSS. Intermediate contacts of each crosspoint in a column are controlled by respective intermediate crosspoint contact selection switches not shown. f

When a vertical and horizontal magnet of croissbar switch 49?. are operated by the particular tens and units digit entered in decoder the six contacts of the corresponding crosspoint are closed. The operation of one of the crosspoint Contact selection switches applies ground however only yto one of the six closed contacts of the selected crosspoint. The other side of each crosspoint contact is connected to an individual code` point in code point eld 46@ so that the entry of a four-digit number in decoder 456 results in the application of ground to only one of the code points in the iield. Each code point in iield 46@ for which a telephone number is assigned will have a jumper J- connected thereto and this jumper threads the transformer rings R- in memory 47? in a pattern that corresponds to the digits of the required telephone number. Each jumper therefore defines digits in a seven, ten, or thirteen digit Word and, accor ingly, memory 470 is a word-organized memory. As describedin Patent 2,614,176, issued to T. L, Dimoud on October 14, 1952, the grounding of a jumper threading a plurality of transformer rings causes a pulsing circuit (not shown) associated with the memory to apply a current pulse to the jumper. The current pulse induces an output voltage in the windings associated with the threaded transformer rings. The `output windings are applied to an output stage @Sti which advantageously may include la plurality of gas tubes for registering and serially transmitting the digits of the output word indicated by the energized jumper. The output stage 48@ is connected to the sender portion of receiver-sender set 393 over cable 307 and lead 308. Signals are passed along cable 367 to operate the frequency selecting contacts of the pushbutton array PB of the multifrequency sender portion of receive -sender 363 in similar fashion yto that in which signals were passed to operate the corresponding contacts PB of outpulser H2. When the seventh, tenth, or thirteenth digit has been transferred from output stage dtl `to operate the appropriate contacts PB of sender 3&3, an end-of-pulsing signal is applied by output stage 48) to lead 30S to operate relay END in the sender. This endof-pulsing signal advantageously may be provided to output stage 4S@ by threading jumper J- through'a transformer ring RE in array 479 lassigned for this purpose. Accordingly, when output stage 4S@ responds to the indication furnished by this core, it applies a groundl to lead 308. Y

Accordingly, it is seen 4that a three-digit cede dialed by a PBX extension user results in the selection of an auxiliary trunk yat the PBX ythat is associated with an idle central office trunk. The auxiliary trunk provides for the registration of the remaining digits and the regeneration of the initial digit of the condensed dialing code. The digits of the condensed dialing code are transmitted to a common translator serving a plurality of different PBXs which translator' includes a plurality of crossbar t switches. The crossbar switches may be wired to provide .a variety of different translations for the condensed dialing codes for each PBX and the codes may be restricted for use by individual PBXS or usable by all PBXs in common, asdesired. The condensed dialing code transt lated by the translator into a conventional seven, ten, or

thirteen digit telephone number code is transmitted back along the same path to the PBX over which the condensed dialing code was furnished and is applied at the PBX to the idle, central office trunk associatedY with Ythe Yauxiliary condensed dialing trunk. After the completion of this transmission, the outgoing central 'ofiice trunk is cut through to the extension user, thereby establishing the normal communications path.

It is understood that the above-described arrangements are merely illustrative of the application of the principles l2 of the invention. Numerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope of this invention.

What is claimed is:

l. A telephone switching system including a central oiiice and at least one private branch exchange served by said central oiice, a plurality of outgoing trunks connecting said private branch exchange to said central otlce, means for obtaining the directory numbers of telephones served by said central oce, and means for transmitting the directory numbers of said telephones served by said central office over said trunks outgoing from said private branch exchange, said last-mentioned means comprising a data link interconnecting said private branch exchange with said central oiiice, means for transmitting one of said telephone directory numbers from said central otlice over said data link to said private branch exchange, and means associated with said data link at said private branch exchange for forwarding said directory number to said central oice over one of said outgoing trunks.

2. A telephone switching system including a private branch exchange, a central oflice switching network and trunks outgoing from said exchange to said switching network, said outgoing trunks normally being operable to control said switching network in accordance with numbers following a preliminary number dialed by an extension user at said private branch exchange, said switching system being characterized by means for seizing one of said outgoing trunks to operate said central oflce switching network incident to the dialing of a number other than said preliminary number comprising means at said private branch exchange for registering a condensed dialing code, said registering means including a plurality of control paths individual to said outgoing trunks, means responsive to the registration of said condensed dialing `code for seizing one of said control paths, circuit means providing extended appearances for said outgoing trunks, means for bridging an extended appearance of one of said outgoing trunks, means for translating said condensed dialing code into a conventional telephone directory number code, and means associated with said translating means for transmitting said telephone directory number code over said extended appearance of said outgoing trunk.

3. A private branch exchange trunk circuit comprising a first selector switch, a plurality of outgoing central oice trunks, a plurality of'auxiliary trunks, said outgoing and said auxiliary trunks being associated with said selector switch, translator means associated with said auxiliary trunks, said translator means having stored therein a plurality of addressed directory numbers, means for reecting at said auxiliary trunks the busy and idle condition of predetermined ones of said outgoing trunks, means responsive to the dialing of a lirst address digit for selecting an idle one of said auxiliary trunks, means responsive to the thaling of additional address digits over one of said Yauxiliary trunks for seizing one of said predetermined outgoing central oice trunks, and means for transmitting over said seized trunk the directory number corresponding to said rst andsaid additional address digits.

4. In a telephone switching system having a first selector for connecting an extension station to any of a plurality of trunks in accordance with a rst digit signaled by said station, the combination comprising means associated with a trunk selected by said rst digit signaled for Aapplying a calling condition to lanother of said plurality of trunks, a translator, a data link connectable to said translator, means including said data link for coupling subsequent digits signaled by said extension station'over said selected trunk to said translator, and means for transmitting digits from said translator over saidV data 1lxl'lnk to said trunk having said calling condition applied ere o.

5. A private branch exchange system having an outwardA switching train including a first selector and a group of outgoing trunks appearing on at least one level of said selector, said trunks normally being selectable by dialing a directing digit associated with said one level, a plurality of auxiliary trunks appearing on at least one other level of said first selector, sleeve circuit means associating 'subordinately-preferred ones of said Voutgoing trunks with predetermined ones of said auxiliary trunks, connector circuit means associated with said auxiliary trunks, said connector circuit being operable to select a terminal on its bank having coordinates determined by two successive digits of a condensed dialing code transmitted over said auxiliary trunk, circuit means extending said sleeve circuit to said connector, means for transmitting an expanded code corresponding to said condensed dialing code over one of said subordinately-preterred outgoing trunks associated with said auxlfary trunk, means responsive to the completion of said last-mentioned transmission for interconnecting directly said last-mentioned outgoing and said auxiliary trunks, and means for locking said interconnecting means under the control of said sleeve circuit.

6. A telephone system including a private branch exchange and a telephone central oince having an outward switching network accessible to said private branch exchange over a plurality of trunks, means for transmitting telephone number codes over said trunks from said private branch exchange to operate said outward switching network at said central oice, said last-mentioned means including means for registering a condensed form of said telephone number codes dialed by an extension user at said private branch exchange, means for preparing one of said trunks incident to the dialing of said condensed code, means i'or transmitting a translated form of said condensed code over said selected one of said trunks, and means responsive to the completion of said code transmitting for establishing a communications switching path from said extension user to said outward switching network over said selected one of said trunks.

7. In a step-by-Step switching system, a rst selector circuit comprising a plurality of trunks distributed over an outgoing level of said selector, each of said trunks having tip, ring, and sleeve appearances on said selector, a plurality of condensed dialing trunks distributed over at least two other Ilevels of said selector, a plurality of connector circuits equal to the number of said condensed dialing trunks distributed over one of said other levels of said selector, a sleeve circuit connecting each of said connectors to a sleeve terminal of one condensed dialing trunk on each of said other levels and to one trunk on said outgoing level of said selector, a digit transmission circuit, a signal path including one of said connector circuits for connecting the tip and ring of said one condensed dialing trunk to said digit transmission circuitto receive the second and third digits of a condensed dialing code, a digit translating circuit coupled to said transmission circuit and responsive to said first, second, and third digits of said condensed dialing code for applying signals to said tip and ring terminals of one of said corresponding outgoing trunks, and means including said transmission circuit responsive to said translating means for connecting said last-mentioned tip and ring terminals to the tip and ring terminals of said one of said condensed dialing trunks.

8. A private branch exchange system having an outward switching train including a rst selector and a group of outgoing trunks appearing on at least one level of said selector, said trunks normally being selectable only by dialing `a directing digit associated with said one level, a plurality of auxiliary trunks appearing on at least one other level of said first selector, sleeve circuit means associating subordinately-preferred ones of said outgoing trunks with predetermined ones of said auxiliary trunks, connector circuit means vassociated with said auxiliary trunks, said connector circuit being operable to select a terminal on its bank having coordinates determined by two 14 successive digits of a condensed dialing code transmitted over `said auxiliary trunk, 'a crossbar switchhavinga plurality of multicontact Vcrosspoints, transmlssion circuit means responsive to the coordinate position of said terminal of said connector rfor operating a corresponding one of -said crosspoints of said crossbar sw-itch, means responsive to the selection of one ot said auxiliary trunks for energizing a Acorresponding contact set of said crosspoints, and means including said transmission circuit means activated by the energization of said last-mentioned contact set of said operated crosspoints for applying an expanded code corresponding to said condensed dialing code over one of said outgoing trunks.

9. An abbreviated-dialing code translator for a private branch exchange having a plurality of extension stations, trunks, and a iirst selector for connecting an extension station to a trunk indicated by a -iirst code digit, said translator comprising -a connector associated with predetermined ones of said trunks for selecting a terminal having coordinates coresponding -to second and third code digits, decoder means, means responsive to the selection of one of said predetermined trunks for registering said iirst code digit in said decoder means, coordinate signaling means responsive to the selection of said connector terminal for registering said second and third digits in said decoder means, a crossbar switch having a plurality of multicontact crosspoints, said decoder being connected to operate a crosspoint of said crossbar switch in accordance with a particular combination of said second and third digits, and means connected to said decoder for energizing a contact of said operated crosspoint in accordance with said iirst code digit.

10. A telephone system including a central oice and a private branch exchange associated therewith by a plurality of trunk lines, a plurality of condensed dialing trunks, means responsive to the dialing of an abbreviated code at said private branch exchange for seizing one of said condensed dialing trunks, means for preparing said central otiice to receive digits over one of said first-mentioned trunk lines, means for transmitting said abbreviated-dialing codes over said condensed dialing trunks to said central oice, translating means at said central oiiice for expanding said abbreviated-dialing codes into telephone number codes of the type suitable for transmission over conventional telephone system trunk circuits, and means including said condensed dialing trunks for transmitting said telephone number codes to said central otiice over said one of said first-mentioned trunk lines.

11. In a telephone system having a private branch exchange of the step-bystep type, an auxiliary trunk circuit, said trunk circuit having an appearance on a level of a iirst selector switch corresponding to the first digit of an abbreviated-dialing code, a plurality of trunks outgoing to a central ott-ice appearing on another level of said irst selector, means responsive to the selection of a trunk on said condensed dialing trunk level of said first selector for seizing control of an associated one of said outgoing central oice trunks, translator means responsive to the dialing of said abbreviated-dialing code for providing a telephone number code transmissible over said outgoing central oce trunk, and means responsive to the receipt of said telephone number code by said central o'ice for establishing a direct transmission path from said outgoing central otrice trunk to said auxiliary trunk circuit appearance on said iirst digit level of said iirst selector.

12. Ina telephone system, a private branch exchange, a central oiiice, a plurality of outgoing trunks connecting said branch exchange to said central oiiice and norm-ally seizable at said exchange on dialing of a predetermined signal at said exchange, a plurality of data linksinterconnecting said exchange and said central oiice, means responsive to the dialing of a different predetermined signal for seizing one of said data links and associating therewith an idle one of .said outgoing trunks, means for registering a condensed dialing code and for transmitting said 15 condensed code over said one data link to said central office, means in said central oce for translating said condensed code into a directory code and for transmitting said directory code back to said exchange, and means at said exchange responsive to receipt thereat of said directory code for applying said directory code to said idle one of said outgoing trunks to said centra-1 oice,

References Cited in the ie of this patent UNITED STATES PATENTS Wicks Mar. 3, 1942 Malthaner et al Sept. 6, 1960 

1. A TELEPHONE SWITCHING SYSTEM INCLUDING A CENTRAL OFFICE AND AT LEAST ONE PRIVATE BRANCH EXCHANGE SERVED BY SAID CENTRAL OFFICE, A PLURALITY OF OUTGOING TRUNKS CONNECTING SAID PRIVATE BRANCH EXCHANGE TO SAID CENTRAL OFFICE, MEANS FOR OBTAINING THE DIRECTORY NUMBERS OF TELEPHONES SERVED BY SAID CENTRAL OFFICE, AND MEANS FOR TRANSMITTING THE DIRECTORY NUMBERS OF SAID TELEPHONES SERVED BY SAID CENTRAL OFFICE OVER SAID TRUNKS OUTGOING FROM SAID PRIVATE BRANCH EXCHANGE, SAID LAST-MENTIONED MEANS COMPRISING A DATA LINK INTERCONNECTING SAID PRIVATE BRANCH EXCHANGE WITH SAID CENTRAL OFFICE, MEANS FOR TRANSMITTING ONE OF SAID TELEPHONE DIRECTORY NUMBERS FROM SAID CENTRAL OFFICE OVER SAID DATA LINK TO SAID PRIVATE BRANCH EXCHANGE, AND MEANS ASSOCIATED WITH SAID DATA LINK AT SAID PRIVATE BRANCH EXCHANGE FOR FORWARDING SAID DIRECTORY NUMBER TO SAID CENTRAL OFFICE OVER ONE OF SAID OUTGOING TRUNKS. 